the login function. id like to know where im going wrong in this

controller

public function login(){

        $this->load->library('session');
        $this->load->model('Model_students');

        $email = $_POST['email'];
        $password = $_POST['password'];


     $data = $this->Model_students->login($email, $password);

        if($data)
        {
            $id=$data[0]->id;
            $first_name=$data[0]->firstname;
            $last_name=$data[0]->lastname;
            $this->session->set_userdata('user_id',$id);
            $this->session->set_userdata('lname',$last_name);
            $this->session->set_userdata('user', $email);
            $this->session->set_userdata('fname',$first_name);
            $this->getImg();
            redirect('Students/homepage');
        }
        else{

            $this->session->set_flashdata('error','Invalid login. User not found');
        }
    }

public function getImg()
{
    $userid=$this->session->userdata('user_id');
    $res=$this->Model_students->getimge($userid);
    $img=$res[0]->userfile;
    $img1=json_decode($img);
    $this->session->set_userdata('img',$img1);
}

model

public function login($email,$password)
        {
            $query = $this->db->get_where('users', array('email'=>$email));
            if($query->num_rows() == 1 )
            {
                return $query->result();

            }

    }

    public function getimge($userid)
        {
            $query = $this->db->get_where('user_images', array('user'=>$userid));
            if($query->num_rows() == 1 )
            {
                return $query->result();

            }


        }

after i sign in using credentials the page redirects to the signin instead of loading the view of the homepage.where could the problem be because it when i run this doesn't work as its supposed to